Reproducibility of linear and angular cephalometric measurements obtained by an artificial-intelligence assisted software (WebCeph) in comparison with digital software (AutoCEPH) and manual tracing method

ABSTRACT Introduction: It has been suggested that human errors during manual tracing of linear/angular cephalometric parameters can be eliminated by using computer-aided analysis. The landmarks, however, are located manually and the computer system completes the analysis. With the advent of Artificial Intelligence in the field of Dentistry, automatic location of the landmarks has become a promising tool in digital Orthodontics. Methods: Fifty pretreatment lateral cephalograms obtained from the Orthodontic department of SRM dental college (India) were used. Analysis were done by the same investigator using the following methods: WebCeph™, AutoCEPH© for Windows or manual tracing. Landmark identification was carried out automatically by Artificial Intelligence in WebCeph™ and with a mouse driven cursor in AutoCEPH©, and manually using acetate sheet and 0.3-mm pencil, ruler and a protractor. The mean differences of the cephalometric parameters obtained between the three methods were calculated using ANOVA with statistical significance set at p<0.05. Intraclass correlation coefficient (ICC) was used to determine both reproducibility and agreement between linear and angular measurements obtained from the three methods and intrarater reliability of repeated measurements. ICC value of >0.75 indicated good agreement. Results: Intraclass correlation coefficient between the three groups was >0.830, showing good level of agreement, and the value within each group was >0.950, indicating high intrarater reliability. Conclusion: Artificial Intelligence assisted software showed good agreement with AutoCEPH© and manual tracing for all the cephalometric measurements.


INTRODUCTION
In the field of Orthodontics, cephalometric radiography is an essential tool for the treatment planning of underlying dental and skeletal discrepancies. 1 It is also a valuable tool to evaluate treatment outcome and research. Conventional/manual analysis involves tracing of anatomic landmarks on an acetate sheet and measurement of the cephalometric parameters.
The technique is time-consuming despite the wide-spread use in Orthodontics, and is largely dependent on the skills and knowledge of the clinician. In this context, errors in landmark identification due to fatigue may occur. 2,3 Recently, cephalometric analysis using digitized software has gained attention and minimized many manual tracing related flaws. Another benefit is the possibility of conducting several analyses in a very short period of time, greatly minimizing human error due to fatigue. [4][5][6] Other advantages of digitally acquired cephalometric imaging can be mentioned, such as a better recognition of the landmarks, image amplification and efficient storage of data. The future scope of using digital imaging in orthodontics is to make teleradiology a reality. 7,8 Research conducted on digital cephalometry has found that the differences between the measurements derived from the digitally located landmarks and the conventional cephalometric radiographs were clinically acceptable, yet the results were Dental Press J Orthod. 2023;28(1):e2321214 found to be statistically significant. Different studies have evaluated the replicability of angular and linear measurements by various digital cephalometric computer programs such as Vistadent, Dolphin, and Quick Ceph. [9][10][11][12][13] A two-dimensional (2D) artificial intelligence driven cephalometric program named "WebCeph™" was programmed and made available as a web based platform for computers and also as a phone application. The most unique feature of WebCeph TM is that it automatically identifies the landmarks using AI (artificial intelligence).
Artificial intelligence can be a useful tool to reduce the time necessary for the final diagnosis and treatment planning.
As errors may occur during landmark identification, it is necessary to verify whether this AI-based software is reliable and reproducible when compared to a previously validated digital software (AutoCEPH © ) and the traditional manual tracing. 14 This study tests the null hypothesis that both linear and angular measurements acquired from two digitalized cephalometric analysis softwares (WebCeph™ and AutoCEPH © ), as well as conventional method of tracing would not disagree to a statistically significant level. For conventional method of tracing, no changes in resolution, contrast or brightness were made before printing. The cephalograms were printed on 8 x 10-in size radiographic film using (Drypix, Fujifilm,Tokyo, Japan) a compatible X-ray printer.
Based on the quantification of the known distance (e.g. 10 mm) between the two fixed points of the ruler present on the cephalostat of the digital x-ray system and on the digital images on the frame, adjustment of the true size of each cephalograph (in millimeters) was carried out.

LANDMARKS IDENTIFICATION AND CEPHALOMETRIC PARAMETERS
Twenty seven anatomical landmarks were marked on a cephalogram by the same investigator to evaluate commonly used cephalometric parameters used by orthodontists. The landmarks used in the study are described in (Fig 1). 1,15,16 Prince TT, Srinivasan D, Duraisamy S, Kannan R, Rajaram K -Reproducibility of linear and angular cephalometric measurements obtained by an artificial-intelligence assisted software (WebCeph) in comparison with digital software (AutoCEPH) and manual tracing method Dental Press J Orthod. 2023;28(1):e2321214   (Table 1 and Fig 1). All linear and angular measurements of the conventional radiographs were recorded using a 0.3mm mechanical lead pencil on an acetate paper using a millimeter ruler and protractor.   Three readings were measured out and the average value was recorded. Excel spreadsheet was used to record the final readings.
To minimize errors due to human fatigue, only 5 cephalograms were analyzed per day both manually and digitally.
Finally, 10 radiographs were randomly selected from the fifty radiographs and manually and digitally retraced, with a 10-day interval between assessments to test intra-observer reliability for analog and digital methods.

STATISTICAL ANALYSIS
Statistical analysis was carried out using software version 26 of the Statistical Package for Social Sciences (SPSS Inc., IBM, Chicago, Illinois, United States).
The cephalometric measurements of each parameter obtained from all the three tracing methods are presented as mean and standard deviation ( Table 2). ANOVA (Analysis of variances) was used to verify any significant difference of cephalometric parameters obtained by the three tracing methods. Data distribution was normal in each group. 1 Bonferroni analysis was use ad hoc. The level of significance was set at p < 0.05. indicated good agreement (Table 3). For the randomly selected 10 retraced radiographs, to assess the intrarater reliability for each tracing technique, the intraclass correlation coefficient (ICC) of the repeated cephalometric measurements was evaluated for 25 cephalometric parameters (Table 4).

RESULTS
The mean and standard deviation of each cephalometric parameter obtained from the final readings were tabulated and subjected to analysis by ANOVA, indicating no statistically significant difference between the cephalometric measurements among the three methods at p<0.05 ( Digital cephalometry provides many advantages in terms of fatigue and ease of application, however, the landmark identification process is operator dependent and in case of multiple cephalometric analysis can be tiring and time consuming. 1,2,5,6,17,18,20,24 With the introduction of AI-based landmark identification software WebCeph™, the process of digitization has become easy and rapid. The main objective for incorporating AI in cephalometrics is to reduce the work load of orthodontists and allow easy access through an online portal for computers and mobile phone from anywhere in the world. 27 AI-based digital softwares require high resolution lateral cephalogram and absence of structures superimposition, because of possible interferences with the algorithm for landmark identification. 26 This disadvantage is not seen in manual tracing as the operator can differentiate and evaluate the structures based on sound knowledge and judgment.

LIMITATIONS
The ability to analyze landmark by AI is solely dependent on radiograph quality and resolution. It is also dependent on internet connection and cannot be accessed from remote areas where network is not available. AI cannot identify or approximate bilateral structures which are superimposed on the radiograph.

FUTURE SCOPE
With the advent of teleradiology, the online based AI software WebCeph™ can be used for both teaching and training from traditional locations and also successfully improving the orthodontic referrals and expertise through technology. It is anticipated the compatibility with mobile devices and availability as a smartphone app. Further 3D based AI algorithms can be developed to construct and automatically identify landmarks and construct the various cephalometric analyses.

CONCLUSION
The Artificial Intelligence software WebCeph™ showed high level of agreement in terms of reliability with earlier validated software AutoCEPH © and manual tracing. The agreement of the softwares for the repeated measurements was found to be adequate, suggesting that it can be used for routine cephalometric analysis and clinical research by the orthodontists.